Post 21 – It’s Contradictory, Complicated & Confusing

As the few of you who have read this blog previously know, over the last few months I have been interested, some would say obsessed, about heating and the amount of energy we use to stay warm.  Additionally, the overarching aim of this blog is to measure and understand, as individuals and householders, how low we have to get our green house gas emissions  so that the planet is not warmed to such an extent that we can no longer live comfortably or maybe even live at all.  I have explored a variety of ways of measuring our personal and domestic emissions but am yet to find a method that I consistently like, that can be used widely, and also makes sense when compared with other measures, such as the cost of energy or amounts of gas and electricity used.

This week I was encouraged in my pursuit of the overarching aim of this blog by the following quote from a researcher at the Collaborative Research Center (CRC) for Low Carbon Living who, when was talking about a recently published study, said ‘A key reason for the study was that in the residential sector, which represents around 30% of global electricity consumption, the underlying composition and drivers of energy use have until now been poorly understood.’  The bit in this quote that I think is really important is the statistic that the residential sector, globally, accounts for 30% of electricity consumption.  To me, that makes it worthwhile that we, as individuals and householders, get our demand for electricity as low as possible.  As an aside, I should add that Collaborative Research Centers don’t just spring up around Australia because someone has a good idea; they are at the ‘heavyweight’ end of the Australian research scene.

Now anyone reading this post may well ask why I didn’t think that the really important bit in the above quote was the bit saying that until now the composition and drivers  of residential electricity use were poorly understood, meaning that now they are well understood.  I eagerly read the rest of the article but it turns out that ‘average’ suburban homes in Sydney with ducted air-conditioning uses 70% more electricity than those without and those with pools use 93% more electricity than those without pools!  The article goes on to say that this information will help policy makers and planners make better informed decisions about electricity demand.  Great! I think most people intuitively know that households with pools and ducted air-conditioning need more electricity than those without.

Now for the confusing and complicated part of this blog.  What are we to make of the following sentence having just read the previous paragraph?

‘Our research has quantified that reverse cycle air conditioners in Australia recover more renewable energy than do all of the millions of rooftop solar photovoltaic (PV) installations.’

This sentence comes from an article by an energy adviser from the Melbourne Energy Institute at the University of Melbourne.  Again, like CRCs, output from the University of Melbourne is also at the serious end of the research spectrum.  So what are we, as ordinary people and ordinary householders, to make of one article that says air conditioning results in greater electricity use and another that says air-conditioners are better than solar?  My response, when I first read this sort of conflicting information, from two equally reputable sources, is to say it’s all too hard and move onto something else but, this time, I have tried to reconcile the apparent contradictions, in the hope that it will lead to greater insights in relation to our own heating issues.

Before I launch into a paragraph or two about what I think the ‘take home’ messages are in these apparently contradictory reports, below is part of an article that is contradictory as far as my experience is concerned.  It confuses me because we try REALLY hard to minimize our heating costs.  It also makes me wonder what on earth I am doing wrong at our place, where I estimate we use an additional 18 kWh of electricity on really cold days with an average of an additional 12 kWh each day over the two coldest winter months (July and August)!  REL and his family, who live nearby, and with whom I discuss such matters, has a similar experience to mine and we both really wish it was different.  So here is the article that could become my new domestic target if only I could work out how it was achieved.

‘As we shiver here in Melbourne, how would you like to reduce your heating costs by up to, say, 70%? If interested, you have to do two things: (1) turn your gas heater to “off” and (2) turn your reverse cycle air conditioner to “on” – on heating mode of course!In my home we did that for the first time this winter. Our savings are remarkable, though not surprising nor different to what others in the community are reporting. As an example, during two particularly blustery days I found I could comfortably heat my house one day with gas at an energy-only cost of A$4.80 and then do it the next day with my air conditioner at a cost of just A$1.50. Our savings across the full heating season will add up to hundreds of dollars.’

OK – this writer heated his house for one day for $1.50!  Let’s say he can buy electricity for $0.255/kWh so he used was about 6 kWh to keep warm for a day.  I am going to hold that measure as a benchmark!

Putting aside the contrast between the electricity used to heat two Victorian houses in winter, I will return to the contradictory messages that I started this post with; air-conditioners and what I think might be the underlying message.

Like all good analyses, it is important to make sure that we are comparing ‘apples with apples’.  In the first article, the discussion was about ducted air-conditioners; in the other article the discussion was about reverse cycle air conditioners.  Now ‘air-conditioner’ usually refers to a cooling-only device whereas ‘reverse cycle air conditioner’ refers to a unit that can both heat and cool.  Reverse cycle air conditioners can have two or three vents or ‘heads’ but often only have one.  The sort of air-conditioner that is talked about in the second article is also usually a ‘split system’ with the working part of the system outside on the ground and the head or vent on the wall or in the ceiling.  So, structurally, these are quite different pieces of equipment but the real difference is in how they perform.

One of the most important ideas to understand is that some heating and cooling devices can use say, 100 watts and give you 100 watts of heating or cooling but others can use 100 watts and give you much more heat (or cool), say 400 watts or even 600 watts.  This difference is called the co-efficient of performance with a higher COP being better.  The ever useful Wikipedia tells us ‘coefficient of performance or COP (sometimes CP) of a heat pump is a ratio of heating or cooling provided to electrical energy consumed’.  Now, something I learnt today when researching for this post is that reverse cycle air-conditioners are, apparently, known as heat pumps in Tasmania and elsewhere in the world.  No wonder I am confused but I am less confused when I think about the technology of the reverse cycle air-conditioners and heat pumps; they both draw heat out of the surrounding air and heat or cool it via a refrigerant.  So, a reverse cycle air conditioner might sometimes, somewhere be called a heat pump but it definitely uses heat pump technology.  I found this diagram a useful aid in understanding the process but you will notice that the measures are in mega-joules.  Just to be clear, joules (J) or mega-joules (MJ) (one million joules) is a pretty universal measurement of energy.  Gas invoices are always in MJ of use whereas electricity invoices are in kWh.  1 MJ equals 3.6 kWh if you ever want to compare the two types of energy.  There are quite a lot of clips about how heat pumps work but here is one if you are interested.

Having mentioned gas, I have to go a step further and talk briefly about gas and the future.  There are a number of analyses around that consistently say that the price of gas is going to rise in the near future; not, it seems, because of concerns about the burning of fossil fuels but because of demand from ‘elsewhere’.

To almost conclude, my take away messages from this post is:

If you live in an urban area in south-eastern Australia, and you are buying a new heater for your home that will be as ‘future proof’ as possible, then buy an electric reverse cycle air conditioner with a COP of a least 4.0 but as high as you can afford.

My additional take home messages, born of experience, are:

• Heat/cool as small an area as possible (bedrooms only need spot heating for a short while, usually just prior to going to bed);
• Properly size the unit for the area to be conditioned;
• Cover windows overnight; use pelmets; double glaze if you can afford it (but watch out for thermal bridges (parked));
• Stop drafts; and
• Insulate walls, floors and ceilings.

This has been a longer post than usual (it just grew somehow) but I am going to close now with the following commentary on President Obama’s recent visit to the Arctic:

“In remarks that bordered on the apocalyptic, Mr. Obama warned that the effects of global warming that have hit the Arctic the hardest would soon engulf the world — submerging entire countries, annihilating cities and leaving fields barren — unless more was done to reduce emissions. Four times in a 24-minute speech, he repeated his assertion that “we’re not acting fast enough.”

Bye for now, Jane